Run for Your Life Flashcards
Label the Diagram
Describe the role of tendons.
Attach muscle to bones. Enable muscles to power joint movement. Not elastic. Made of white fibrous tissue - bundles of collagen fibres so strong.
Describe the role of ligaments.
Holds the position of bones and controls and restricts movement in the joint. Made of yellow elastic tissue and collagen which gives both strength and elasticity and flexibility. Connects bone to bone.
Describe the role of cartilage.
Cartilage protects bones within joints. Hard but flexible. Elastic and able to withstand compressive forces. Made of cells called chondrocytes within an organic matrix of collagen fibres. Very god shock absorber. 2 types: hyaline cartilage and white fibrous cartilage.
Describe the role of bone.
Supports the body structure and protect vital organs, strong and hard.
Bone cells embedded in a matrix of collagen fibres and calcium salts is light. Very strong under compression forces.
Describe the role of synovial fluid.
Acts as lubricant
Describe how a pair of antagonistic muscles work to move a joint.
The pair of muscles create opposite forces. When one relaxes (stretches), the other contracts (shortens).
What are the extensor and flexor muscles?
- Extensor muscle: the muscle which contracts to extend the joint.
- Flexor muscles: The muscle which contracts to flex/ bend the joint/ limb.
What are the 3 main types of muscle?
- Smooth muscle
- Cardiac muscle
- Striated, Voluntary or Skeletal Muscle
Describe smooth muscle.
Under the control of the involuntary nervous system. Causes slow contractions of many internal organs, i.e. arteries, intestine. Long and spindle shaped cells, each
with their own nucleus. No striations/stripes (parallel groves). Contractions are slow & long lasting, and the fibres fatigue very slowly.
Describe cardiac muscle.
Only found in the heart. Striated/striped muscle. Interconnected fibres to ensure a co-ordinated wave of contraction. Contracts spontaneously (myogenic). Does not fatigue. Capable of short contractions over a long time period (your whole life).
Describe Striated, Voluntary or Skeletal Muscle.
Muscle attached to the skeleton & involved in locomotion.
Under the control of the voluntary nervous system. It contracts rapidly, but fatigues quickly. Capable of strong contractions.
Describe the muscle tissue.
Muscle is made up of bundles of muscle fibres, surrounded by connective tissue. Each muscle fibre is one cell which is multinucleate and striated. Inside the muscle fibre cell are numerous myofibrils. Each myofibril is composed of repeated contractile units called sarcomeres. The two types of protein within these are actin and myosin.
Describe what happens when muscle contracts.
Contractions are brought about by co-ordinated sliding of the protein filaments over each other in the sarcomere. The actin moves between the myosin. This shortens the length of the sarcomere, and hence the length of the muscle.
Why do muscles appear striped (striated) under the microscope?
The actin and myosin overlap. Where actin filaments occur on their own, there is a light band on the sarcomere. Where myosin filaments occur on their own, there is an intermediate-coloured band. Where both actin and myosin filaments occur, there is a dark band.
Define sarcoplasm.
The cytoplasm of a muscle cell.
Describe the sequence of events that occurs at the neuromuscular junction.
A nerve impulse arrives from a motor neurone. Acetylcholine is released from the end of the neurone. Acetylcholine results in the release of calcium ions (Ca2+) from the sarcoplasmic reticulum. Ca2+ diffuse into the sarcoplasm surrounding the myofibrils.
Describe the Sliding filament theory.
- Before contraction the myosin binding sites on the actin are blocked by tropomyosin. So the myosin head which has ADP and Pi bound to it cannot bind to myosin
- Ca2+ binds to the troponin causing it to move and pull on the tropomysoin which shifts postions, exposing the mysoin binding sites on the actin molecule. The myosin head binds with the myosin binding sites on actin and an actinmyosin cross bridge forms.
- When the myosin head binds to the actin, ADP + Pi on the myosin head are released. Myosin changes shape and head nods forward. Actin moves over the myosin. The actin moves towards the centre of the sarcomere, and shortens the overall sarcomere length.
- An ATP molecule binds to the myosin head causing another shape change. The myosin head detaches from the actin. This activates ATPase in the myosin head, which also needs Ca2+ to work. The ATP is hydrolysed ADP + Pi are formed and energy is released. The energy returns the myosin head to its original position.
Label the diagram.
Describe what happens when the muscle relaxes.
The muscle is no longer stimulated by the motor neurone. Ca2+ is pumped back into the sarcoplasmic reticulum by active transport. This requires ATP. The troponin moves back to its original position and the tropomyosin moves to back to cover and block the myosin binding sites on the actin.
Describe what happens to muscles in rigor mortis.
After death, ATP production stops. With an absence of ATP, the myosin heads will remain attached to the actin (the cross-bridges stay intact). The muscle is unable to relax and remains ridged. The cross-bridges are only broken when the muscle fibres start decomposing.
Describe the role of calcium ions in the contraction of skeletal muscles.
- Calcium ions released in response to nervous stimulation of the muscle set up contraction of the sarcomeres
- Calcium ions bind to troponin changing the shape of the molecule
- This change in shape pulls the tropomyosin away from the myosin binding sites on the actin molecules exposing them
- The myosin heads now bind, setting up the contraction
- Calcium ions are also needed for the action of the ATPase enzyme in the myosin heads, which enables the heads to return to their original resting position
Explain why the presence of ATP and it’s hydrolysed form are so important for the contraction of striated muscle.
- The ATP binds to the myosin head, and the release of energy when it is hydrolysed allows the head to return to the resting position
- The bonding of ADP and Pi results in changes in the shape of the myosin head so it can bind to the actin binding site
- The release of the ADP and Pi results in another shape change which results in the bending of the myosin head causing the actin to slide over the myosin
- ATP is also needed as the energy supply for the calcium pump which returns calcium ions to the sarcoplasmic reticulum, ending the contraction.
Write the overall word and balanced chemical equation for respiration.
Glucose + Oxygen –> Carbon Dioxide + Water + energy
C6H12O6 + 6O2 –> 6CO2 + 6H2O + 38 ATP
Draw a mitochondrion
What are the 5 processes in Aerobic Respiration?
- Glycolysis
- The Link Reaction
- Krebs Cycle
- The Electron Transport Chain
- ATP synthesis & Chemiosmosis
Where in the cell does glycolysis occur?
In the cytoplasm (or sarcoplasm of muscle cells).
What substrate is needed for Glycolysis and where does it come from?
Needs glucose (hexose monosaccharide) as substrate.
* Could come straight from bloodstream.
* Glycogen in muscle or liver cells is converted to glucose.
Describe Glycolysis
- Glycogen is rapidly hydrolysed to release the stored α-glucose by breaking the 1,4 and 1,6 glycosidic bonds - known as glycogenolysis.
- Glucose (6C) is phosphorylated using the 2 phosphates released from the hydrolysis/dephosphorylation of 2 molecules of ATP. The hydrolysis releases energy and the phosphates are transferred between the molecules by a kinase enzyme. The phosphorylated glucose then splits to form 2 intermediate (3C) compounds (GALP) each with a phosphate attached.
- Each GALP is oxidised/dehydrogenated to form 1 molecule of pyruvate (3C). The 2 hydrogen atoms removed from each GALP are used to reduce 1 molecule of NAD to form reduced NAD or NADH + H+.
- Each GALP is also dephosphorylated. The phosphate is used to phosphorylate one molecule of ADP to form ATP - known as substrate-level phosphorylation. The reaction requires a kinase enzyme. In total 4 ATP are made, however 2 are used in the first step so there is a net gain of 2 overall.
Describe the link reaction.
- Pyruvate is decarboxylated and one molecule of CO2 is released
- Pyruvate is oxidised and dehydrogenated. The 2 hydrogen atoms are used to reduce 1 molecule of NAD to form reduced NAD or NADH + H+
- 1 molecule of Acetyl CoA (2C) is produced and enters the Krebs cycle
Where in the cell does the Krebs cycle take place?
In the mitochondrial matrix.
Describe the Krebs cycle.
- One molecule of Acetyl CoA is combined with 1 4C compound (Oxaloacetate). The 6C compound Citrate is formed.
- The 6C compound is decarboxylated and one molecule of CO2 is released
- The 6C compound is oxidised and dehydrogenated to form the 5C compound (α-Ketogluterate). The 2 hydrogen atoms are used to reduce 1 molecule of NAD to form {reduced NAD / NADH + H+}
- The 5C compound is decarboxylated and one molecule of CO2 is released
- 1 molecule of ATP is created by substrate-level phosphorylation
- The 5C compound is oxidised and dehydrogenated to form a 4C compound (Oxaloacetate). 4 hydrogen atoms are used to reduce 2 molecules of NAD to form 2 molecules of {reduced NAD / NADH + H+}
- 2 hydrogen atoms are used to reduce 1 molecule of FAD to form reduced FAD. The 4C compound is reformed.
Describe the process of ATP synthesis at the electron transport chain.
- The reduced co-enzyme (reduced NAD or reduced FAD) brings 2 hydrogen atoms to the ETC; electron carrier proteins embedded in the inner mitochondrial membrane. The reduced co-enzyme is oxidised when it passes its 2 hydrogen atoms to the first electron carrier in the ETC.
- Each hydrogen atom is split into an H+ ion and an electron. The electrons pass down the ETC between the electron carriers in a series of redox reactions. The energy level of the electron falls and energy is released.
- The energy is used to pump H+ ions through the electron carriers into the intermembrane space.
- As the H+ ions accumulate, an electrochemical gradient is created and the pH of the space falls and becomes acidic.
- H+ ions diffuse down the electrochemical gradient through a stalked particle back into the mitochondrial matrix. As they diffuse through, they activate ATP synthase which phosphorylates ADP to create ATP in a condensation reaction.
- To maintain the electrochemical gradient, each H+ ion re-joins with an electron to reform a hydrogen atom. Two hydrogen atoms bond to ½O2 to form one molecule of water (2H+ + 2e- + ½O2 -> H2O).
The oxygen acting as the final electron acceptor on ETC is reduced.
This method of ATO synthesis is called oxidative phosphorylation.
Describe what happens if there is a lack of oxygen in the mitochondrion.
Effect on the electrons: (think about oxygen)
- Without oxygen, there is no final electron acceptor for the electron transport chain. The electrons are unable to leave the final electron carrier. Electrons cannot move down the electron transport chain and so redox reactions stop and energy is no longer released.
- Without the movement of electrons, reduced co-enzyme is unable to become oxidised by passing its electrons to the first electron carrier in the electron transport chain. Oxidised co-enzyme (NAD and FAD) is unable to be regenerated and sent back to glycolysis, the link reaction and the Krebs cycle. Without oxidised NAD and FAD, these three processes stop and ultimately aerobic respiration stops.
Effect on the hydrogen ions:
- Without oxygen, the H+ ions that have diffused down through the stalked particle have no molecule to bind to. Therefore, as they start to accumulate in the matrix the electrochemical gradient disappears and no further H+ ions diffuse down through the stalked particle.
- Without the energy from the redox reactions, H+ ions are not pumped into the intermembrane space and so no electrochemical gradient is created. Therefore, H+ ions do not diffuse down through the stalked particle.
As a result of steps 1 and 2, ATP synthase is unable to phosphorylate ADP to create ATP. ATP production stops.
Explain the role of carrier molecules in the electron transport chain.
- Recieve hydrogen from reduced NAD/ FAD.
- Break hydrogen into H+ and electrons.
- Electrons are transferred by a series of redox reactions.
- The energy is used to pump H+ into the intermembrane space.
What is the effect on aerobic respiration of oxygen demand in cell excedding the supply.
Without oxygen to accept the H+ ions and electrons (act as the final electron acceptor), the electron transport chain stops. The reduced NAD produced in glycolysis, link reaction and Krebs cycle are not able to be oxidised.
Describe the process of Anaerobic Respiration. (Involves glycolysis)
- Glucose is converted to 2 intermediate (3C) compounds (GALP). Each GALP is oxidised to form 1 molecule of pyruvate. 2 hydrogen atoms are removed per GALP.
2.The 4 hydrogen atoms removed reduce 2 molecules of NAD to form 2 reduced NAD (NADH + H+). - Each reduced NAD (NADH + H+) is oxidised and 2 molecules of pyruvate are reduced to form 2 molecules of lactate (lactic acid).
- The oxidation of reduced NAD reforms (oxidised) NAD. This can then be used to receive further hydrogen atoms from the oxidation of GALP. This keeps glycolysis going.
- The continued break down of glucose to pyruvate enables the formation of a net gain of 2 ATP per molecule of glucose by substrate level phosphorylation.
Describe the consequence of lactate accumulating in cells.
Lactate forms lactic acid in solution. This reduces the pH of cells. The enzymes that catalyse glycolysis are inhibited and glycolysis stops. Muscle contraction and physical activity stops.
Describe the effect of the products of anaerobic respiration on enzymes.
The H+ ions from lactic acid accumulate in the cytoplasm. They neutralise the negatively charged R groups of amino acids in the active site of an enzyme. This prevents the substrate being attracted to, and binding to the active site. Enzyme substrate complexes can’t form.
How is lactate removed?
Lactate moves into the blood and is transported to the liver. It is oxidised and converted back to pyruvate. The pyruvate is then fully oxidised via the link reaction, Krebs cycle and the electron transport chain to form CO2 and water. Some pyruvate can be converted back into glucose and transported back to the muscles to be stored as glycogen (gluconeogenesis). This is known as the Cori cycle.
What is the excess O2 requirement after exercise known as?
The oxygen debt or post-exercise oxygen consumption (sometimes EPOC)
What is aerobic capacity?
The ability to take in, transport and use oxygen.
What are the 2 types of skeletal muscles?
- Fast twitch muscle fibres
- Slow twitch muscle fibres
Describe fast twitch muscle fibres (role).
- Specialised for rapid, intense contractions
- The ATP used in these contractions is produced almost entirely from anaerobic respiration.
Describe slow twitch muscle fibres (role).
- Specialised for slower, sustained contraction.
- Can cope with long periods of exercise
- Carry out a large amount of aerobic respiration.
List the characteristics of fast twitch muscle fibres.
- Pale pink/ white
- Few capillaries
- Little myoglobin
- Large glycogen stores
- Lots of sarcoplasmic reticulum
- Fatigue easily
- Few mitochondria
List the characteristics of slow twitch muscle fibres.
- Deep red
- Lots of capillaries
- Lots of myoglobin to store O2
*Not much stored glycogen - Little sarcoplasmic reticulum
- Doesn’t fatigue easily
- Many mitochonidra
What is myoglobin?
- Protein similar to haemoglobin - made of 1 chain rather than 4
- It has a much higher affinity for oxygen than haemoglobin
- Acts as an oxygen store in muscles
- Dark red in colour which gives slow twitch muscle fibres their distinctive colour.
What happens during exercise?
- Breathing rate/ ventilation rate increases
- Breathing depth increases
- Cardiac output increases
Describe inhalation.
Describe exhalation.
Name the region of the brain that controls breathing.
The ventilation centre in the medulla oblongata.
At rest, state the most important stimulus controlling breathing rate and depth.
The concentration of dissolved CO2 in arterial blood (via the drop in pH).
Describe how an increase in exercise brings about an increase in breathing rate and depth.
- Increase in dissolved CO2 in blood plasma due to increased respiration which creates carbonic acid (H2CO3).
- Carbonic acid dissociates into hydrogen ions and hydrogen carbonate ions. This lowers the pH of the blood. (CO2 + H2O -> H2CO3 -> H+ + HCO3)
- Chemoreceptors in the walls of the aortic arch and carotid artery detect the increase in CO2/ drop in pH in the blood. Impulses are sent to the ventilation centre in the medulla oblongata.
- Chemoreceptors in the ventilation centre of the medulla oblongata can also detect the drop in pH.
- An increased number of / more frequent impulses are sent from the ventilation centre via a sympathetic neurone to the intercostal muscles & diaphragm to stimulate more frequent and stronger contractions.
State the purpose of the more frequent and deeper breaths.
This maintains a steep concentration gradient of CO2 between the alveolar air and the blood. This ensures efficient removal of CO2 from the blood and uptake of O2 into the blood.
Describe the other stimuli that will increase breathing rate and depth when starting exercise.
- The motor cortex of the brain controls movement. As soon as exercise begins impulses from the motor cortex are sent to the ventilation centre in the medulla oblongata.
- Stretch receptors (mechanoreceptors) in tendons and muscles involved in movement send impulses to the ventilation centre.
- Temperature receptors (thermoreceptors) detect the increase in blood temperature and send impulses to the ventilation centre.
- Chemoreceptors detect a drop in O2 concentration in the blood and send impulses to the ventilation centre. These are rarely stimulated under normal circumstances.
What is the control of CO2 concentration an example of?
Homeostasis operating via negative feedback.
State the name of the equipment used to measure lung volumes.
Spirometer
Define tidal volume.
The volume of air that is breathed in and out in one breath
Define vital capacity.
The maximum volume of air a person can inhale and exhale
Define breathing rate.
The number of breaths in a set time period. Measured in breaths per minute.
Define minute ventilation.
The volume of air taken into the lungs in one minute.
Describe how to calculate tidal volume.
Measure the vertical distance between a peak and trough. Convert to a volume using the calibration scale. Measure multiple breaths to calculate a mean average.
Describe how to calculate vital capacity.
Measure the vertical distance between the highest peak and the lowest trough. Convert to a volume using the calibration scale.
Describe how to calculate breathing rate.
Count the number of troughs in a set period of time. Units are breaths min-1.
Describe how to calculate minute ventilation rate.
Multiply the (mean) tidal volume (dm3) by the breathing rate (number of breaths per minute). Units are dm3min-1.
Describe how to calculate oxygen consumption.
Identify a trough at the start of the trace and a trough a known time period away i.e. 1 minute. Draw a trend line between the 2 troughs. From the second trough, draw a horizontal line back to line up with the first trough – form a triangle. Calculate the difference in volume between the first trough and the horizontal line.
Describe how to calculate the rate of oxygen consumption.
Divide the oxygen consumption by the time over which it falls i.e. dm3min-1 or cm3s-1
Define myogenic.
The heart muscle can contract without any external nervous stimulation. The stimulation is generated from within the muscle. The stimulation brings about depolarisation of the heart muscle.
Describe the process of a heart beat.
- The sinoatrial node (SAN) generates an electrical impulse that results in a wave of depolarisation spreading over the atria (through the atrial walls) causing them to contract (atrial systole). Blood is forced into the relaxing ventricles.
- The impulse arrives at the atrioventricular node (AVN) where it is delayed by 0.13 seconds. The rest of the impulse is blocked by the non-conducting layer between the atria and ventricles.
- After the slight delay, the impulse travels down to the heart apex through the Purkyne fibres in the bundle of His within the septum of the heart.
- The impulse travels along the Purkyne fibres which branch out within the ventricular muscle. Contraction of the ventricles (ventricular systole) occurs from the apex and travels up in the direction of the atria. This causes the blood to be pushed up and out of the heart through the aorta and pulmonary artery.
State the importance of the non-conducting layer between the atria and the ventricles.
To prevent the impulse travelling to the muscle at the top of the ventricles. This would cause the ventricles to contract from the top downwards forcing the blood to the bottom of the heart and not up and out.
State why it is important for the impulse to be delayed in the AVN.
This ensures that the atria have finished contracting and that the ventricles have filled with blood before they then contract.
State how the electrical activity of the heart can be detected and displayed.
An electrocardiogram (ECG) measures the change in potential difference in heart muscle cells. Measured in millivolts (mV).
